Photos from South Korea's official news agency show Mark Lippert with blood on his hand and holding his bleeding face. A man shouted "No to war training!" before attacking him, the Yonhap news agency reported.
The ambassador was slashed on the face and wrist by the man who was screaming that the rival Koreas should be unified, South Korean police said Thursday, according to the Associated Press. Lippert was attacked with a 10-inch fruit knife, police told ABC News. His assailant was arrested, according to Robert Ogburn, an official at the U.S. embassy in Seoul, who said the U.S. strongly condemned the "senseless act of violence."
In a televised briefing, Chung Nam-sik of the Severance Hospital said 80 stitches were needed to close the facial wound, which was more than 4 inches long and 1 inch deep. He added the cut did not affect his nerves or salivary gland.
President Obama called Lippert to tell him that "he and his wife Robyn are in his thoughts and prayers, and to wish him the very best for a speedy recovery,” according to National Security Council spokesperson Bernadette Meehan.
Lippert previously held positions at the Department of Defense from May 2012 until September 2014, according to the embassy website.
ABC's Joohee Cho and the Associated Press contributed to this report.